1. Field of the Invention
The present invention relates in general to a feeding device for the preneedle punching of nonwoven fabrics.
2. Description of the Related Art
FIG. 1 depicts a conventional feeding device for the preneedle punching of fiber batt, in which bulky fiber batt 1 is conveyed to a feed-in roller 3 by a belt conveyer 2, where the fiber batt 1 is compressed by the roller 3, conveyed to the location between a stripper plate 4 and a bed plate 5, where the fiber batt is punched and tangled by plural needles 7 of a needle board 6, and then fed out by feed-out rollers 8. The bulky fiber batt 1 is compressed by the feed-in roller 3, but expands after the feed-in roller 3, before the stripper plate 4 and the bed plate 5. The fiber batt expands to a hunched shape, with a part of fiber batt accumulated at the inlet of the tangling zone between the stripper plate and the bed plate. As a result, the nonwoven fabrics have fish-scale-shaped traces or even creases thereon. The quality of the produced nonwoven fabrics is poor. Furthermore, the feed-in roller 3 and the needles 6 are separated by a distance in which the fiber batt is easily deformed due to draft. To prevent the draft and deformation of the fiber batt, the linear speed of feed-out rollers 8 is necessarily set faster than that of the feed-in roller 3. Generally, the draft ratio of the feed-out rollers 8 to the feed-in roller 3 is 1.2-2. If the draft ratio is small, then the fiber batt tends to accumulate at the inlet of the tangling zone. If the draft ratio is large, then the fiber batt is too tensed and is still deformed due to draft so that the produced nonwoven fabrics are of poor quality. Furthermore, thick fiber batt tends to accumulate at the inlet of the tangling zone between the stripper plate and the bed plate. Therefore, the stripper plate and the bed plate of a conventional preneedle punching machine generally are separated by a large distance to receive thick fiber batt. However, such an arrangement causes a vertical vibration of the fiber batt in the tangling zone so that the structure of the produced nonwoven fabrics is deteriorated.
U.S. Pat. No. 5,031,289 discloses a feeding device for a preneedle punching machine which includes an upper belt conveyer and a lower belt conveyer. The front edges of the belt conveyers have triangular noses extending towards the space between the stripper plate and the bed plate. This arrangement reduces the distance in which the fiber batt is not secured. However, the draft and deformation of the fiber batt cannot be totally eliminated.
Japanese Patent No. 5-163659 discloses a method and device for producing soft and bulky nonwoven fabrics, in which the bed plate is discharged and a plane belt conveyer is used instead. In the patent, the needles cannot penetrate through the fiber batt. The fiber batt (especially the bottom fiber batt) is not tangled very well. The method and device provides light punches and is only suitable for producing soft and bulky nonwoven fabrics.
A cylinder type of preneedle punching machine is provided to improve the problems of draft and deformation of fiber batt, wherein the stripper plate and the bed plate are replaced with an upper cylinder and a lower cylinder. The upper and lower cylinders have holes thereon, and have needle mounts inside. This type of preneedle punching machine does avoid the draft and deformation of fiber batt. However, the density of the needles is not adjustable because the needles are necessarily arranged to pass through the holes of the cylinders. Therefore, fiber batt of low internal cohesion cannot be tangled very well by this type of preneedle punching machine. Besides, the needle board of the preneedle punching machine needs to move in a trochoidal path so that this type of preneedle punching machine is too complicated in structure. Furthermore, the meshes of the nonwoven fabrics are too large. The fine needle punching process cannot eliminate the punching traces.
Another type of preneedle punching machine is provided with a brush conveyer, also used for improving the problems of draft and deformation of fiber batt, wherein the above-mentioned bed plate is replaced with the brush conveyer. The use of brush conveyer does improve the problems of draft and deformation of fiber batt. However, the soft fiber batt supported by the brush conveyer tends to sway so that the uniformity of the fiber batt during the preneedle punching operation is poor. As a result, the quality of the nonwoven fabrics is poor. Furthermore, vertical fiber is brought to the brushes by the needles, held by the brushes and thus fails to be tangled together with previous fiber. The fiber batt cannot be effectively tangled. As well, an external force is needed to strip the tangled fiber batt from the brush conveyer. The external force can possibly cause the draft and deformation of nonwoven fabrics. Therefore, this type of machine generally applies to the velour needle punching process.
An object of the present invention is to provide a feeding device for preneedle punching of nonwoven fabrics that solves the above-mentioned problems.
The feeding device of the present invention includes a stripper plate, a bed plate, a linear belt conveyer and a plurality of needles. The linear belt conveyer passes through a space between the stripper plate and the bed plate and conveys fiber batt to the space. Then, the needles punch and tangle the fiber batt in the space.
In the present invention, the linear belt conveyer continuously and actively holds the fiber batt during the preneedle punching process so that the distance between the stripper plate and the bed plate is reduced by 50%. As a result, the damage to the fiber batt by the airflow from the rapid motion of the needle board, and the vibrations of the fiber batt in the tangling zone, are effectively avoided. Furthermore, the elongation of the fiber batt before the tangling operation is minimized, thereby promoting the quality of resultant nonwoven fabrics.